Cathode ray tubes are now commonplace as a result of the rapid increase in the use of computers and the like. Since the surface of a cathode ray tube is relatively dark, it serves to reflect glare from the surrounding environment, hence reading of the information on the cathode ray tube can become difficult. This glare problem was to a large extent overcome by the addition of a glare filter as described in U.S. Pat. No. 4,253,737 issued to Patrick Brennan and Eric Thomson.
An equally and possibly more serious problem is the radiation of electro-magnetic energy from the area of the display tube and the generation of a static electrical field adjacent to the cathode ray tube. While a good deal of attention has been directed toward the suppression of electro-magnetic radiation, it has not been completely eliminated. The current levels of radiation eminating from cathode ray tubes are generally well below the threshold of injury to operators. However, emitted radiation still exists and can cause a security problem by permitting the clandestine interception of and the interpretation of the intercepted information.
Currently electro-magnetic radiation is reduced by a metal, for example stainless steel, screen embedded or sandwiched between conformed glass plates positioned in front of the display tube. While these systems perform the desired function, they do not necessarily reduce glare. Further the inherent structure of the screen being displaced from the display tube can result in shadows, Newton's rings or Moire patterns.
Static electricity has, in recent months, received a good deal of attention as a potential health hazard. In one instance, a study was conducted in Norway wherein there was an increased incidence of face rash among operators of video display terminals, including cathode ray tubes. This is attributed to the fact that the operator is positioned in the static field created by this cathode ray tube so that the operator becomes charged. With a charge on the operator, oppositely charged dust and other airborne pollutants are attracted to the operator so that any irritants, bacteria, or virus are "delivered" to the operator as a result of the induced static charge.
Similarly, the face of the cathode ray tube carries a static charge thus a particulate matter such as dust, smoke particles or the like having an opposite electric charge are attracted to the surface of the tube. When the mesh antiglare filter such as described in U.S. Pat. No. 4,253,737 is utilized, it is necessary to remove the filter from the cathode ray tube in order to clean the face.